Automatic parallelization of grid-based applications for the iPSC/860

Abstract

The need to invest considerable time and effort to modify programs written in FORTRAN 77 so that they run in parallel has impacted the use of MIMD computers like the iPSC/860. The difficulty associated with very large codes has provided motivation for a number of research efforts to develop tools that reduce the parallelization effort. Very recently, these efforts have progressed to the point where semi-automatic parallelization is possible for a very important class of problems, the so called grid-based applications.

Three examples of such tools are FORGE 90, Pfortran and Fortran Linda. This paper describes success in using these tools to parallelize 3 grid-based applications. All three tools were used on a numerical weather prediction benchmark. In addition FORGE 90 was applied to two other programs from the NAS collection of parallel benchmarks. All 3 programs are of the order of a few thousand lines of FORTRAN 77 code and were converted to run in parallel using FORGE 90 in a day or two. Parallelization by hand took 2–3 week while the use of Pfortran and Fortran Linda each required about a week. Comparison of performance results for the various methods indicates that FORGE 90 achieves about 50 to 65% of the performance of the hand-coded version while Pfortran and Linda achieves 75 to 90% of the same performance.